Name: ______________________________________________________ Period: ____________

Conservation Questions & Problems

Match the formulas to the appropriate terms

1. _____ kinetic energy

2. _____ gravitational potential energy

3. _____ work

4. _____ power

5. _____ momentum

6. _____ impulse

7. _____ force

a) fΔtb) W/tc) ½ mv2

d) mve) m•Δv/tf) fd g) mgh

Match the definitions with the appropriate terms.

8. _____ The type of simple machine that turns rotating motion into linear motion using a cylindrically-shaped ramp is called a ______.

9. _____ An incline that decreases the input force by increasing the distance over which the fore is applied is a ______.

10. _____ A rotating lever with teeth that allows torque to be transferred from one point to another is a ______.

11. _____ A simple machine that works as input and output arms rotate about a fulcrum is a ______.

12. _____ A block and tackle system is a simple machine using ______ ______ ______ to create a mechanical advantage.

a) gearb) screwc) ropes and

pulleysd) levere) ramp

Match the definitions with the appropriate terms.

13. _____ The amount of work an object can do is ______ energy.

14. _____ The mechanical advantage an object possesses because it is moving (“energy of motion”) is ______ energy.

15. _____ The energy responsible for making most household appliances work is ______ energy.

16. _____ The energy responsible for causing a balloon to expand is ______ energy.

17. _____ The total potential and kinetic energy is called ______ energy.

18. _____ Energy released when the nuclei of light atoms are combined or nuclei of heavy atoms are split is ______ energy.

19. _____ Hot objects contain more ______ energy than cold objects.

20. _____ Energy is stored in molecules in the form of ______ energy.

21. _____ Electromagnetic energy can be referred to as ______ energy.

22. _____ The law of ______ ______ ______ states that the total energy in the universe is constant.

a) nuclear b) potential c) conservation of

energyd) chemical e) mechanical f) electrical g) kinetic h) thermal i) radiant j) pressure

Name: ______________________________________________________ Period: ____________

Match the definitions with the appropriate terms.

23. _____ The ratio of output force to the input force is the ______ ______.

24. _____ What a machine does for you is called the ______.

25. _____ A machine that alters the magnitude or direction of a force is known as a ______ ______.

26. _____ A device created by humans to do something useful is a ______.

27. _____ Everything you do to make a machine work is ______.

28. _____ When a force is applied and motion occurs in the direction of the force ______ is done.

29. _____ The rate at which energy flows is called ______.

30. _____ The output work of a machine is always less than the input work because of the energy lost to ______

31. _____ A ratio of energy input to energy output is the ______ of the machine.

32. _____ An ______ ______ involves objects bouncing off each other with no loss in kinetic energy.

33. _____ In an ______ ______, objects change shape or stick together, and some kinetic energy is converted to other forms of energy such as heat, deformation or friction.

34. _____ An ______ causes a change in momentum. It is a product of a force and the amount of time the it is applied.

a) efficiencyb) simple

machinec) elastic

collisiond) powere) inputf) machineg) inelastic

collisionh) mechanical

advantagei) frictionj) outputk) workl) impulse

Match the definitions with the appropriate terms.

35. _____ Energy contained in the food we eat is often measured in units called food ______.

36. _____ The unit of measurement for work is the ______.

37. _____ The unit of power is the ______.

a) jouleb) Wattc) calories

38. The word “work” has a very specific meaning in physics. Why is it that no work is done if a force of 1000N is applied to a brick wall if it doesn’t move?

39. Stacy eats a bowl of corn flakes for breakfast and then rides her bicycle to school. When Stacy pedals the bike, a small taillight flashes for highway safety. Draw an energy diagram showing the energy transfer that must occur to make the taillight work. (Remember all energy on Earth starts with the sun.)

40. A car going twice as fast requires four times as much stopping distance. What is it about the kinetic energy formula that accounts for this fact?

Name: ______________________________________________________ Period: ____________

41. Harold bounces on a trampoline.a. At what point in his motion does he have the highest gravitational potential energy?

b. At what point does he have the highest kinetic energy?

c. What happens to the energy when he sinks down into the trampoline?

42. In one 8 hour workday, a forklift operator lifts a total of 100,000 N of boxes. Each box must be lifted to a height of 1.5 m and carried an average of 10 m to the shipping dock. What is the net work done against gravity?

43. Steve lifts a 5-kg toolbox 0.5 meters off the ground in one second.a. Compare the amount of work that would be done on Earth to the amount that would be done on the moon.

b. Where would he use the most power?

44. Sometimes in large cities underground cables can become frayed, causing the cable insulation to catch fire. This fire can ignite the build-up of gasses under the streets and cause an explosion that sends manhole covers flying as much as 15.2 m in the air. These manhole covers can weigh as much as 136 kg.a. What is potential energy of a 136 kg manhole cover when it reaches 15.2 m above the ground?

b. What is the speed (in m/s) of the manhole cover when it hits the ground

45. A 1120 kg car is traveling with a velocity of 40 m/s. The car has ______________ energy. Calculate it.

46. A cinder block is sitting on a platform 20 m high. It weighs 79 N. The block has ______________ energy. Calculate it.

Name: ______________________________________________________ Period: ____________

47. There is a bell with a mass of 19.4 kg at the top of a 45 m high tower. The bell has ______________ energy. Calculate it.

48. You serve a 2.1 kg volleyball at 30 m/s. The ball has ______________ energy. Calculate it.

49. What is the difference between energy and power?

50. The diagram below represents a 5-kg mass placed on a frictionless track at Point A and released. Assume GPE is zero at Point E.

a. Calculate the GPE at Point A.

b. Compare the KE of the object at Point B to the GPE at Point D.

c. Compare the KE of the object at Point B to the KE of the object at Point C.

d. Calculate the speed at Point C.

51. The graph shows a ball rolling down a hill then back up the other side. The ball begins at Point A.a. At what letter does the ball have the greatest kinetic energy?

A

CE

DB

20 m

15 m

10 m

5 m

0 m

Name: ______________________________________________________ Period: ____________

b. Which letter shows the ball when it has the maximum potential energy?

c. Which letter shows the ball when it has the least potential energy?

d. Why is Point G slightly lower than Point A? In other words, why couldn’t the ball go back to the same height at which it started?

52. Bicycles can have efficiencies as high as 85%. What happens to the remaining 15% of the input energy?

53. Erik and Patsy are working out in the weight room. Erik lifts a 50 lb barbell over his head 10 times in 1 minute. Patsy lifts a 50 lb barbell over her head 10 times in 30 seconds.a. Who does the most work? How do you know?

b. Who delivers the most power? How do you know?

54. Big Bertha and Skinny Stanley run up a steep hillside. Bertha is twice as massive as Stanley, and Stan got to the top in half the time.a. Who did the most work? How do you know?

b. Who delivered the most power? How do you know?

55. What is the efficiency of an escalator that uses 200 J of electrical energy for every 20 J of energy gained by the riders?

Name: ______________________________________________________ Period: ____________

56. Michelle, who has a mass of 75 kg, runs up a 3 m staircase in 5 seconds.a. How much work did she do?

b. What was her power rating in Watts?

c. If she uses 10 calories (41870 J) of energy when she runs up the stairs, what is her efficiency?

57. A ball having a weight of 1.5 N is dropped from a height of 4 meters. (Neglect air friction) a. What net force is acting on the ball after being dropped?

b. What is the potential energy just before being dropped?

c. What is the kinetic energy just before hitting the ground?

d. What mechanical energy is lost just before it hits?

58. A ball having a weight of 1.5 N is dropped from a height of 4 meters. The average frictional force is 0.2 N. a. What net force is acting on the ball after being dropped?

b. What is the potential energy just before being dropped?

c. What is the kinetic energy just before hitting the ground?

d. What mechanical energy is lost?

Name: ______________________________________________________ Period: ____________

59. In problem 58 above, from what height must the ball be dropped to have twice the kinetic energy as from 4 meters? Explain.

60. In problem 58 above, from what height must the ball be dropped to have twice the velocity as from the 4 meters? Explain.

61. A 1 kg mass moving at 1 m/s has a totally inelastic collision with a 0.7 kg mass. What is the speed of the resulting combined mass after the collision? Compare the final kinetic energy to the initial kinetic energy.

62. A cart of mass 1 kg moving at a speed of 0.5 m/s collides elastically with a cart of mass 0.5 kg at rest. The speed of the second mass after the collision is 0.667 m/s. What is the speed of the 1 kg mass after the collision? Compare the total momentum and total kinetic energy before and after the collision.

63. A 10 gram bullet is shot from a 500 gram gun at a speed of 230 m/s. Find the speed and kinetic energy of the bullet and the gun. Assume that the momentum and energy of the escaping gasses are negligible.

64. Two carts with masses of 4 kg and 3 kg move toward each other on a frictionless track with speeds of 5.0 m/s and 4.0 m/s respectively. The carts stick together after the colliding head on. Find the final speed of the carts.

65. Jennifer, who has a mass of 50.0 kg, is riding at 35.0 m/s in her red sports car when she must suddenly slam on the brakes to avoid hitting a deer crossing the road. She strikes the seatbelt, bringing her body to a stop in 0.500 s. What average force does the seat belt exert on her?

66. If Jennifer had not been wearing her seat belt and not had an air bag, then the windshield would have stopped her head in 0.002 s. What average force would the windshield have exerted on her?

Name: ______________________________________________________ Period: ____________

67. A cyclist doubles her speed. What happens to her momentum?

68. Consider a bulldozer at rest and a hockey player moving across the ice.a. Which has the greater mass?

b. Which has the greater velocity?

c. Which has the greater momentum? Why?

69. Howard tries to jump from a rowboat to a nearby dock. Why is this a bad idea even if the distance seems short enough to jump?

70. Padding is used in baseball gloves, goalie mitts, football helmets and gymnastic mats. Explain the physics behind the use of padding in these cases.

71. What is the secret to catching a water balloon without breaking it? Why?

72. Cars that crumple in a collision are safer than cars that rebound when they hit. Why?

73. Would you rather be hit with a 700 g puppy traveling at 40 m/s or a 1.5 g M&M traveling at 20,000 m/s? Why?

74. A 2000 kg truck moving at 5 m/s runs into a concrete wall. It takes 2 seconds for the truck to completely stop. What is the magnitude of force exerted on the truck during the collision?

75. A force of 400 N is exerted on a baseball by the bat for .003 s. What is the impulse of the baseball?